XLR connectors are used for most professional audio connections and must be wired correctly to ensure that no phase errors occur and that all cables are compatible. XLR connectors are wired as follows:

Unbalanced Lines

1. Ground (shield) to Ground (Shield)

2. Hot (+ or Red) to Signal (Centre core)

3. Cold (- or Blue) to Ground (connect to pin 1)

It is essential that all connections are correctly made; both centre cores must be connected for a balanced line to work correctly. The XLR is a 3-pin connector and the outer shell of the plug is linked to the ground pin too. When wiring an XLR to a Jack plug the wiring code is as follows:

Balanced Lines

XLR Pin 1 to Sleeve of Jack (Ground)

XLR Pin 2 to Tip of Jack (Hot)

XLR Pin 3 to Ring of Jack (Cold)

If the Jack is unbalanced, as before Pin 3 and Pin 1 of the XLR must be connected together.